									(IMPLEMENTED MODES: API/PAGE/EMBED/EMBED-API/THIRD_PARTY/FLEX)
	[legacy] Removed in 2.1.19.
	[next]
		The rewrite of above to allow more features and better performance.
		[variants]
			SINGLE_THREADED 		(PAGE, EMBED)
			MULTI_THREADED			(PAGE)
		[status]: STABLE (applies to PAGE-ST, default)
	[next_rolling]
		Improvements to the 'next' branch that haven't been merged yet.
		[variants]
			MULTI_THREADED			(PAGE)
		[status]: ALPHA/INDEV
	[ytapi]
		Extraction via YouTube's own API.
		[variants]
			SINGLE_THREADED			(API)
		[status]: ALPHA
	[ytapi_rolling]
		Improvements to the 'ytapi' branch that haven't been merged yet.
		[variants]
			MULTI_THREADED			(API)
		[status]: ALPHA
	[ytiapi_rolling]
		Extractor for YouTube's universal client backend.
		[status]: ALPHA
	[flex]
		Extraction using heavy scraping and no parsing.
		[status]: ALPHA (FLEX)
